1. Field of the Invention
The present invention relates to a fold-up grandstand formed of successive elements including steps for establishing rows of neighboring seats at different heights, evenly distributed from the top to the bottom of the grandstand, each element being capable of being housed respectively under the previous one whilst surmounting the next one in the folded up position of the grandstand whilst, in the unfolded position, in which each element is completely extracted from the previous one and located in front of it, each row of seats is offset with regard to the previous one located at a higher level and also with regard to the one which is after it at a lower level.
2. Description of the Prior Art
Embodiments of this type are already known in which a plurality of telescopic elements, together forming a staircase-type structure, is designed to be deployed or folded up, the elements nesting in one another whilst being associated with means for controlling their movements, especially in order to tend to provide a perfectly rectilinear relative displacement of these various elements whilst maintaining their parallelism in any position. By way of example, reference may be made, in order to illustrate such an embodiment, to FR-A-2 651 822 of the Applicant Company, or to DE-A-2 709 150 or even to U.S. Pat. No. 4,193,229, in which, however, the mechanisms adopted are less effective than in the first case, the parallelism of the elements not being suitably provided and risking, when opening just as when closing the grandstand, creating prejudicial jamming between these successive elements.
It is, however, noted, even with the arrangements envisaged in the aforementioned French patent, that the result obtained is still not optimal, it sometimes not being possible for the structure of the grandstand to prevent lateral loads which are exerted on the elements with respect to one another, particularly if the ground on which the grandstand is placed is not strictly flat and uniform, from bringing about a more or less limited offset between the successive elements during their relative translational movements, during movements for opening and closing this grandstand.